It's an experimental novel comprising short non-sequential plot elements (although they are ordered alphabetically, presumably for the author's convenience).
Or possibly it's a dictionary?
Anyway, you don't have to read it from front cover to back cover as do sad gits like me. You can just dip in here and there, look up a nautical term you've heard, and enjoy some amusing dits and examples of Forces Humour. Dark Blue, yes, but also Jungly Green, Purple, Light Blue and of course Black.
And it has about 159 of Jack Tar's euphemisms for sexual intercourse. My favourite bon mot's "Receiving swollen goods". What's yours?